Abstract
One of the main consequences of chaos is that transport is enhanced with respect to the fluid at rest, where only molecular diffusion is present. Considering long times and spatial scales much larger than the length scale of the velocity field, particles typically diffuse with a diffusion constant, usually much bigger than the molecular one. Nevertheless there are some important physical systems in which the particle motion is not a normal diffusive process: in such a case one speaks of anomalous diffusion. In this paper, anomalous diffusion is experimentally studied in an oscillating two-dimensional vortex system. In particular, scalar enhanced diffusion due to the synchronization between different characteristic frequencies of the investigated flow (i.e., resonance) is investigated. The flow has been generated by applying an electromagnetic forcing on a thin layer of an electrolyte solution and measurements are made through image analysis. In particular, by using the Feature Tracking (FT) technique, we are able to obtain a large amount of Lagrangian data (i.e., the seeding density can be very high and trajectories can be followed for large time intervals) and transport can be characterized by analyzing the growth of the variance of particle displacements versus time and the dependence of the diffusion coefficient on the flow characteristic frequencies.
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Antonio Cenedese: He received his M.Sc.(Eng) in Mechanical Engineering in 1966 from University of Rome ‘La Sapienza’. He also received his M.Sc.(Eng) in Aerospace Engineering in 1969 from the same University. From 1969 to he worked in as a professor in 1994 in University of Rome, Salerno, L’Aquila and since 1986 he is a full professor of University ‘La Sapienza. His research interests are Fluid Mechanics, Image Analysis applications applied to Flow Measurements, Geophysical Flows, Environmental Hydaraulics, Two-dimensional Turbulence and Biomedical Flow.
Stefania Espa: She received her M.Sc.(Eng.) degree in Environmental Engineering in 1996 from University of Rome ‘La Sapienza’ and her Ph.D. in Environmental Engineering in 2000 from the same University. After obtaining M. Sc., she worked as a Post Doc and teaches Environmental Hydraulics at University ‘La Sapienza’. Her current research interests are Fluid Mechanics, Flow Measuring Techniques, Scalar Transport, Geophysical Flows and Two-dimensional Turbulence.
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Espa, S., Cenedese, A. Anomalous diffusion and lévy flights in a two-dimensional time periodic flow. J Vis 8, 253–260 (2005). https://doi.org/10.1007/BF03181503
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DOI: https://doi.org/10.1007/BF03181503